React-router: Test on multiple React versions

[mjackson]

I'd like to run our tests on multiple versions of React in CI, if we can.

• Travis supports build matrices which we can use to run multiple jobs with different environment variables, so that should help.
• npm supports a --prefix config option that we can use to change (I believe) the location where it looks for package.json and node_modules.

So we may be able to use these 2 features in combination to do something like this in our Travis config:

env:
  - NPM_PREFIX=react-15
  - NPM_PREFIX=react-16
install:
  - npm install --prefix=$NPM_PREFIX

It seems a little hacky, and there would probably be some bugs to work out. But it might work.

[timdorr]

We've got this set up on React Redux if you want to steal some ideas: https://github.com/reduxjs/react-redux/tree/master/test @cellog set it up for us.

[mjackson]

Ah, I see. Instead of using a build matrix you copy all of the source files into a dir with a package.json that specifies the version of React you want to test against. That's a great approach, and doesn't feel quite as hacky. It also seems like it'd be a little more portable if we decide to switch to yarn in the future instead of npm.

[cellog]

Quick chime in: this was the only way I found to do it that didn't have the npm equivalent of dll hell. If the way you implement it is similar, let me know, I would be willing to abstract that into an external package for testing against multiple versions of external deps

[mjackson]

I got a quick start on this in the multi-versions branch, but nowhere near finished yet. The basic idea was to install different versions of React + their dependencies in the /react directory, then use a REACT_VERSION environment variable in the Jest config to setup modulePaths to find React in the right place.

This approach required me to remove react and react-dom from each dir in packages because Jest gives precedence to the local node_modules dir. This caused a few other things to break.

I wonder if there's a good way to tell Jest to search modulePaths before the local node_modules. That would be great in this case.

[umidbekkarimov]

I resolved it using yarn with jest:

1. Install multiple versions of react, react-dom, react-test-renderer and enzyme adapters.
2. Redirect requires in jest setup file.
3. Add multiple test scripts.
4. Add extra scripts to CI script.

[justsml]

Dang, this is a bit late.

But here's how I switch between versions for testing:

#!/bin/bash
# ./test.sh
cd ${PROJECT_FOLDER:-./test}

# switch to v15
sed -i -E 's/"react": ".*",/"react": "^15.0.0",/' package.json
npm install 
react-scripts test --env=jsdom

# switch to v16.6
sed -i -E 's/"react": ".*",/"react": "16.6.0",/' package.json
npm install 
react-scripts test --env=jsdom

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.